Application of generalizability theory to evaluate the Kessler Psychological Distress Scale and distinguish between enduring and dynamic distress

Objectives: Nowadays, the number of older people is increasing rapidly, both in absolute figures and as a proportion of the population, which makes the maintenance of psychological well-being among aging population imperative. Neuropsychological distress may promote cognitive impairment and impact on the health of older people, which makes accurate assessment of distress an important clinical and research issue. The Kessler Psychological Distress Scale (K-10) is a widely used instrument used to measure individual distress. However, the ability of K-10 to distinguish between enduring and dynamic distress symptoms, and the generalizability of its scores, have not been investigated in older populations using appropriate methodology. Method: Generalizability theory (G-theory) was applied to differentiate enduring and dynamic distress and examine the reliability of K-10 in a sample of 201 adults (43% males) aged 70 to 90 years old who participated in Sydney Memory and Ageing Study. The data were collected biennially over ten years. Results: The K-10 scale showed strong reliability (Ga=0.81, Gr=0.89) in assessing enduring distress and its assessment scores were generalizable across occasions and older adults. Most of distress symptoms represented by K-10 items were enduring. Limitations: Generalizability of these findings may be limited to older adults. Conclusions: The K-10 appears more suitable to evaluate enduring distress in aging populations over time, which is important for interventions targeting older adults’ mental health given its scores will likely capture enduring changes in neuropsychological health before and after interventions.